Billions of tons of coal-fired power station waste, called fly ash, are dumped in long term landfill sites worldwide each year. High carbon fly ash, which has a carbon content above 1%, has found little commercial use. Most high carbon fly ash is disposed in landfill sites. Because the fly ash has toxic components, use in landfill present a potential environmental risk in light of the potential for leaching of such species.
In contrast, low carbon content fly ash has found many applications in the construction industry. Many companies have transformed low carbon fly ash into valuable eco-minerals on an industrial scale, with no waste stream. Beneficial uses of low carbon content fly ash are found in the cement and concrete industries, which account for over 50% of low carbon fly ash use.
Fly ash has also attracted polymer scientists and engineers. It is mainly used to substitute traditional, more expensive fillers and extenders in the manufacture of polymers, rubbers, coatings and concrete products. Reportedly, these ash-polymer matrices exhibit higher mechanical strength, improved rheological properties, corrosion resistance, reduced aging rate, etc. While fly ash benefits certain polymeric products, polymers also contribute to the advanced utilization of fly ash. For example, polymers have been used as heavy metal stabilizers through chelating reactions for fly ash to reduce the potential health risks.
Despite the many advantages fly ash provides for polymer composites, such beneficial uses are very limited compared to the others, both in academic research and market. Boral Material Technologies Inc. (BMTI) is one of the few companies to commercialize the ash-polymer matrices. BMTI's Celceram™ series are among the several commercial products available in the market. These products are typically used in carpet backings and plastic pipes to reduce the cost of using certain fillers and expanders. Some patents include U.S. Pat. No. 6,916,863, U.S. Pat. No. 7,241,818, U.S. Pat. No. 7,879,144 for the use of fly ash in polymer composites.
Though the analysis of EPA suggests some of the beneficial uses of fly ash are generally safe, numerous lawsuits have been filed against such use in residential applications and production sites of related materials. People complain of suffering adverse health effects after exposure to the fly ash products and show concerns on their carcinogenicity.
There remains a need in the art to make beneficial use of fly ash, and particularly high carbon content fly ash. The present invention provides a method for agglomerating fly ash with polymer or crosslinked polymer network, the agglomerates protecting against leaching of undesirable, toxic species from the fly ash.